U.S. patent application number 10/516354 was filed with the patent office on 2006-08-10 for routing method and network structure.
Invention is credited to Fabio Longoni, Pedro Serna.
Application Number | 20060176872 10/516354 |
Document ID | / |
Family ID | 29596064 |
Filed Date | 2006-08-10 |
United States Patent
Application |
20060176872 |
Kind Code |
A1 |
Serna; Pedro ; et
al. |
August 10, 2006 |
Routing method and network structure
Abstract
The present invention relates to a method and network system for
changing a routing path between a first data network and a mobile
station attached to a second data network. The said first data
network comprises at least one first network node. The second data
network comprises at least a second network node and a third
network node. The routing path comprises before said change said
first network node, said second network node and said third network
node, and after said change said first network node, and said third
network node. According to the method of the invention the method
comprises a step of transferring an information element from said
second network node to said third network node, wherein said
information element comprises an identification element of said
first network node. The method is preferably used for routing of
paging response messages to International Mobile Subscriber
Identity (IMSI) paging request messages in a GSM/EDGE Radio Access
Network (GERAN) or Universal Terrestrial Radio Access Network
(UTRAN) that supports Iuflex functionality.
Inventors: |
Serna; Pedro; (Santander,
ES) ; Longoni; Fabio; (Malaga, ES) |
Correspondence
Address: |
ROBERT M BAUER, ESQ.;LACKENBACH SIEGEL, LLP
1 CHASE ROAD
SCARSDALE
NY
10583
US
|
Family ID: |
29596064 |
Appl. No.: |
10/516354 |
Filed: |
May 31, 2002 |
PCT Filed: |
May 31, 2002 |
PCT NO: |
PCT/IB02/01960 |
371 Date: |
July 28, 2005 |
Current U.S.
Class: |
370/351 ;
370/401 |
Current CPC
Class: |
H04W 40/36 20130101;
H04W 68/12 20130101; H04W 8/24 20130101; H04W 92/02 20130101 |
Class at
Publication: |
370/351 ;
370/401 |
International
Class: |
H04L 12/28 20060101
H04L012/28 |
Claims
1. A method for changing a routing path between a first data
network and a mobile station attached to a second data network said
first data network comprising at least one first network node, said
second data network comprising at least a second network node and a
third network node, said routing path comprising before said change
said first network node, said second network node and said third
network node, said routing path comprising after said change said
first network node, and said third network node, said method
comprising a step of transferring an information element from said
second network node to said third network node, wherein said
information element comprises an identification element of said
first network node.
2. A method according to claim 1, wherein said information element
is transferred directly from said second network node to said third
network node.
3. A method according to claim 1, wherein said information element
is transferred from said second network node to at least one fourth
network node in said first data network and then from said fourth
network node to said third network node.
4. A method according to claim 1, wherein said information element
is transferred from said second network node to at least one fourth
network node in said first data network, then from said fourth
network node to a fifth network node in said first data network,
and the from said fifth network node to the third network node.
5. A method according to claim 4, wherein said fourth network node
in said first data network has a serving-network-node function for
said second network node before said change, and said fifth network
node in said first data network has a serving-network-node function
for said third network node (26) after said change.
6. A method according to claim 4, wherein said first network node
is related to a packet-switched domain of said first network and
said fourth network node is related to a circuit-switched domain of
said first network, or vice versa.
7. A method according to claim 1, wherein said second network node
has a serving-network-node function in said second data network for
said mobile station before said change, and said third network node
has said serving-network-node function in said second data network
for said mobile station after said change.
8. A method according to claim 7, wherein said third network node
has a drift-network-node function before said change.
9. A method according to claim 4 wherein a plurality of first and
fourth and fifth nodes communicates in parallel with said second
network node before said change, and with said third network node
after said change.
10. A method according to claim 1, comprising a further step of
saving said information element or said identification element to a
data storage device communicating with said second network node
before said step of transferring said information element to said
third network node.
11. A method according to claim 1, comprising a further step of
saving said information element or said identification element to a
data storage device communicating with said third network node (26)
after said step of transferring said information element to said
third network node.
12. A method according to claim 1 wherein said second data network
is a Radio Data Network (RDA).
13. A method according to claim 1 wherein said second data network
comprises a Global System for Mobile Communications (GSM), Enhanced
Data Rates for GSM Evolution Radio Access Network (GERAN) and/or a
Universal Terrestrial Radio Access Network (UTRAN).
14. A method according to the claim 13, wherein said second network
node is related to said GERAN and said third network node is
related to said UTRAN, or said second network node is related to
said UTRAN and said third network node is related to said
GERAN.
15. A method according to claim 2 wherein said identification
element of said first network node is included in a "FORWARD SRNS
CONTEXT" message sent from said second network node to said third
network node.
16. A method according to claim 3, wherein said identification
element of said first network node is included in a "RELOCATION
REQUIRED" message transferred from said second network node to said
fourth or fifth network node, respectively, and is further included
in a "RELOCATION REQUEST" message transferred from said first or
fourth network node or fifth network node, respectively, to said
third network node.
17. Use of a method according to claim 1 for routing response data
answering request data from said mobile station to said first
network node, said request data originating at said first network
node in said first data network, said request data having been
routed along said routing path before said change, said response
data being routed along said routing path after said change.
18. A method according to claim 17, wherein the request data
comprise a paging request message and the response data comprise a
paging response message.
19. A method according to claim 8, wherein said first network node
and said third network node are related in common to a
packet-switched network domain or to a circuit-switched network
domain.
20. Use according to claim 12, wherein the paging request message
comprises an International Mobile Subscriber Identity (IMSI) of the
mobile station.
21. A data network system comprising first data network with at
least a first network node and a second data network with at least
a second network node and a third network node said second network
node being adapted to control a connection between a mobile station
and said first network node, said connection being routed through
said second network node, said third network node communicating
with said second network node and said mobile station, and being
adapted to either allocate at least one communication channel
between said mobile station and said third network node for said
connection under the control of said second network node, or, upon
a transfer of control data relating to said connection from said
second network node to said third network node, control said
connection independently from said first network device, wherein
said second network node is additionally adapted to transfer an
identification element related to said first network node in said
second data network from said second network node to said third
network node.
22. A data network system according to claim 21, wherein the second
network node is adapted to transfer said information element
directly to said third network node.
23. A network system according to claim 21, further comprising a
fourth network node in said first data network, wherein said second
network node is adapted to transfer said information element to
said fourth network node and said fourth network node is adapted to
transfer said information element to said third network node.
24. A network system according to claim 23, further comprising a
fifth network node in said first data network, wherein said fourth
network node is adapted to forward said received identification
element to said fifth network node, and said fifth network node is
adapted to forwarding said identification element to said third
network node.
25. A network system according to claim 21, wherein said second
network node communicates with a storage device and is adapted to
save said identification element in said storage device.
26. A network system according to claim 21, wherein said third
network node communicates with a storage device and is adapted to
save said identification element in said storage device.
27. A network system according to claim 21, wherein said first data
network is a core network and said second data network is a Radio
Access Network (RAN).
28. A network system according to claim 27, wherein said second
data network comprises a GERAN and a UTRAN.
29. A network system according to claim 27, wherein said second
network node is related to said GERAN and said third network node
is related to said UTRAN, or said second network node is related to
said UTRAN and said third network node is related to said
GERAN.
30. A network system according to claim 24 wherein a plurality of
first and/or fourth and/or fifth nodes communicates in parallel
with said second network node and/or with said third network
node.
31. A network system according to claim 21, wherein said first
network node is an Mobile-services Switching Center (MSC), and said
second and third network nodes each are either a Radio Network
Controller (RNC) or a Base Station Controller (BSC), and said forth
and fifth network nodes are SGSNs.
32. A network device for operation in a radio data network, adapted
to establish, maintain and release a connection between a mobile
station attached to the radio data network and a second network
device in a second data network, and transfer control data to a
third network device operating in said radio data network, said
control data serving to establish or maintain a connection between
said mobile station and said second network device, wherein said
network device is additionally adapted to transfer to said third
network device an identification element related to said second
network device.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a routing method and to a
data network system. It also relates to a network device for
operation in a radio data network.
BACKGROUND OF THE INVENTION
[0002] Modern radio data networks evolve towards network
architectures that support packet-switched (PS) services and the
Internet Protocol (IP) in all instances from the mobile station to
the core network. However, circuit-switched (CS) services will have
to be supported as well since most subscribers use equipment that
works according to previous CS standards like GSM.
[0003] Currently developing third generation project partnership
(3GPP) communication network standards support both PS and CS data
services. Their architecture and location and mobility management
will be shortly reviewed in the following. This will lead to the
problem underlying the present invention.
[0004] a) General Network Architecture
[0005] A network according to these standards comprises a core
network (CN), radio access networks (RAN), and mobile stations (MS)
attached to a RAN. A RAN of a 3G-communication network may either
comply with the Universal Terrestrial RAN (UTRAN) architecture of
the Universal Mobile Telephony System (UMTS). Alternatively, a RAN
of a 3G-communication network may comply with the GSM/EDGE Radio
Access Network (GERAN) architecture. The GERAN architecture
provides services comparable to the UTRAN architecture of UMTS
while still supporting the pre-existing GSM (Global System for
Mobile Communication) architecture.
[0006] b) UTRAN Architecture
[0007] In the UTRAN architecture the RAN is divided into a
plurality of Radio Network Subsystems (RNS) each controlled by a
Radio Network Controller (RNC). The RNC is a logical node in the
RNS in charge of controlling the use and the integrity of the radio
resources. Each RNC is connected to a set of Node B elements. A
Node B element is the physical unit for radio transmission and
reception in cells. The main task of the Node B element is the
conversion of data to and from a Mobile station. A cell is a radio
network object that can be uniquely identified by the Mobile
station from a (cell) identification that is broadcast over a
geographical area by the Node B element.
[0008] Inside the UTRAN, the RNCs of the Radio Network Subsystems
can be interconnected together through Iur interfaces. Iur
interfaces can be conveyed over a direct physical connection
between RNCs or virtual networks using any suitable transport
network.
[0009] The communication interface between the UTRAN and a
connected Core Network (CN) is an Iu interface. Depending on
support of packet switched data or circuit switched data the Iu
interface will be an Iu.sub.PS or an Iu.sub.CS interface,
respectively.
[0010] c) GERAN Architecture
[0011] In the general GERAN architecture, which much resembles the
UTRAN architecture, the RAN is divided into a plurality of Base
Station Systems (BSS) each controlled by a Base Station Controller
(BSC). The function of a BSC resembles that of the RNC in a UTRAN.
Each BSC is connected to a set of Base Transceiver Stations (BTS).
The main task of the BTS is, like that of a Node B in a UTRAN, the
conversion of data to and from the UE.
[0012] Inside the GERAN, the BSCs of the Base Station Subsystems
can be interconnected together through Iur-g interfaces. Iur-g
interfaces can be conveyed over a direct physical connection
between BSCs or virtual networks using any suitable transport
network.
[0013] Communication between a GERAN BSC and a UTRAN RNC is handled
using an additional Iur-g interface.
[0014] The GERAN architecture supports the Iu interface to a
connected CN but may alternatively also allow communication with
the CN through A and Gb interfaces. The A interface is a connection
point between a BSC and CN for circuit-switched connections. The Gb
interface is a connection point between a BSC and CN for
packet-switched connections. This allows a GERAN to offer
packet-switched (PS) services in a PS domain using the Iu and Gb
interfaces as well as circuit-switched (CS) services in a CS domain
using the A interface.
[0015] Since GERAN supports the Iu interface between a RAN node and
a Core Network node, a GERAN may connect to the same GSM/UMTS CN as
a UTRAN.
[0016] d) Core Network Architecture
[0017] On the side of the CN a common PS-domain Core Network can be
used for both mentioned types of Radio Access Networks (RAN), the
GERAN and the UTRAN.
[0018] The term PS-domain refers the packet-switched data services
introduced into GSM networks using a standardized overlay general
packet radio service (GPRS) network. Packet-switched communication
uses short bursts of information that use a channel only for a
short period of time. Devices attached to the PS domain are
assigned an IP (Internet Protocol)-type address and are always on.
Data is sent to and from the address, routed using standardized
protocols. The network is essentially an extension of Internet.
Routers determine the path that each packet takes to its
destination. Upon arrival, individual packets, which may be out of
sequence, are put back into order by a packet assembler.
[0019] In the PS-domain a Serving GPRS Support Node (SGSN) keeps
track of the location of an individual MS and performs security
functions and access control. The SGSN is connected to the GERAN
base station system through a Gb or Iu.sub.PS interface and/or to
the UTRAN through an Iu.sub.PS interface.
[0020] In the CS-domain a Mobile-services Switching Center (MSC)
controls the communication between the GERAN Base Station System
(BSS) or a UTRAN RNS and the fixed networks.
[0021] The term CS domain refers to the circuit-switched signaling
and to a switching network based on GSM. Circuit-switched
communication sets up a limited-duration, continuous point-to-point
connection, using a dedicated channel to transmit and receive data.
As long as the channel is connected, no one else can use it; and
the user must initiate a new connection each time data is sent or
received.
[0022] The MSC provides a digital exchange able to perform all
necessary functions needed to handle calls to and from mobile
subscribers located in the MSC area, such as registration,
authentication, location updating, handovers, and call routing to a
roaming subscriber. Specifically, the MSC provides the call
handling necessary to cope with the mobile nature of the
subscribers, e.g. paging. A MSC is connected to a GERAN BSS through
an A interface and to a UTRAN RNS through an Iu.sub.CS
interface.
[0023] In order to enhance the network performance recent Iu
communication interfaces allow an Intra-domain connection of RAN
nodes to multiple Core Network (CN) nodes. That is, in a GERAN or
in a UTRAN a BSC or a RNC, respectively, may connect to multiple CN
nodes. The term "intra-domain connection" refers to a connection
between RAN nodes and CN network nodes within a PS-domain or within
a CS-domain, respectively. This mode of interface operation is
called Iuflex. The Intra Domain Connection of RAN Nodes to Multiple
CN Nodes provides a routing mechanism (and other related
functionality), which enables the RAN nodes to route information to
different CN nodes within the CS or PS domain, respectively.
[0024] In addition, in network systems supporting Iuflex, pool
areas are formed of a plurality of RAN node service areas. The term
pool area refers to an area within which a MS may roam without need
to change the serving CN node, i.e. the serving SGSN or the serving
MSC. The pool-areas of the CS and of the PS domain are configured
independently with the granularity of RAN node service areas. A
Iuflex pool area may be served by one CN node or by a plurality CN
nodes in parallel. All the cells controlled by a RAN node (RNC or
BSC) belong to the same one (or more) pool area(s).
[0025] e) Location and Mobility Management
[0026] Mobility Management (MM) activities are needed for
attachment, detachment and for location updates. As a MS attached
to a RAN moves from one cell to another, it has to be ensured that
the connection to the MS is maintained. As the MS moves, tracking
of its position is performed using location management functions.
Tracking may be performed on the cell level, the level of a
Routeing Area (RA) containing several cells, or on the level of the
Service area containing several RAs.
[0027] The MM activities depend on the mode the MS is operated in.
For instance, two basic operational Radio Resource Control (RRC)
modes of a GERAN MS are idle mode and connected mode. The connected
mode can be further divided into service states, which define what
kind of physical channels the MS is using. For instance, the MS may
be in in a GRA PCH state. In this state the MS monitors a paging
channel (PCH) and can be located by the MSC with the resolution of
a GERAN Registration Area. A rregistration area is an area in which
a MS may roam without a need to perform location registration. In
that case, the user does not need to signal every cell change but
still keeps its Radio Resource Control (RRC) context (RRC
connection), while it would loose it by moving to the IDLE
state.
[0028] Location with higher resolution down to the cell level is
performed by the GERAN. An MS in a RRA_PCH state is said to be
camping on a cell. This state will hereinafter also be named more
generally a RRA_PCH state, since for a UTRAN MS there is a
corresponding URA_PCH state. URA refers to a UTRAN Registration
Area. RRA means Radio Registration Area, be it a GRA or URA.
[0029] Location management provides mechanisms, among others, for
cell selection. One important class of location management
procedures comprises handover procedures. A handover is a process
in which the RAN changes the radio transmitters or the radio access
mode to provide bearer services maintaining a defined service
level. Handover may be initiated by the network based on radio
frequency (RF) criteria as measured by the MS or the Network
(signal level, Connection quality, power level propagation delay)
as well as traffic criteria (e.g. current traffic loading per cell,
interference levels, maintenance requests, etc.).
[0030] There are two types of handover: hard handover and soft
handover. A hard handover is a category of handover procedures
where all existing radio links in the MS are abandoned before new
radio links are established. Soft handover is a category of
handover procedures where radio links are added and abandoned in
such a manner that the MS always keeps at least one radio link to
the RAN. Soft handovers may fully be performed within the RAN,
without involving the core network. For instance, a MS moving from
a first cell towards a second cell may have to communicate with two
or more Node B nodes to ensure maintenance of the connection. A
soft handover may be performed as soon as a certain Node B node is
not anymore necessary to keep up the radio link of the MS to the
RAN.
[0031] Relocation procedures may or may not involve a radio
handover. An SRNS relocation procedure moves the Iu reference point
between the CN and the RAN on the RAN side from a first RNC to a
second RNC. Before relocation, the first RNC is the Controlling RNC
(CRNC) or Serving RNC (SRNC) while the RNC of the second cell is a
Drift RNC (DRNC). The function of the DRNC is controlled by the
SRNC using the Iur interface. Corresponding terms are used for the
GERAN (SBSC, DBSC). By relocation, the role of the serving RNC
(SRNC) in relation to a mobile station moves from the first to the
second RNC.
[0032] In the following, a problem arising from the present network
architecture will be addressed.
[0033] The increased flexibility of the Iuflex functionality
introduces problems that have not been solved to date, for instance
in CS paging. Paging a MS for circuit-switched services is executed
by an MSC. A paging request is sent from the MSC to the BSC serving
the MS. The BSC translates the incoming paging request message into
one radio paging request message per cell. In case of an IMSI
paging message the MSC uses in the paging message the International
Mobile Subscriber Identity (IMSI) of the user as the user
identification. IMSI paging is mostly used when the MSC does not
have knowledge of the Temporary Mobile Station Identity (TMSI) that
is normally used for paging.
[0034] In a GERAN or UTRAN, however, that implements the Iuflex
functionality, in a CS paging procedure, the serving MSC sends a
paging request to a serving BSC/RNC (SBSC) that already may have a
PS signalling connection to the MS. The SBSC sends the paging
request via an Iur-g interface to drifting BSC/RNCs (DBSCs/DRNCs)
that control the cell in the RRA (URA/GRA) the MS is registered.
The DBSC sends the request to further BTSs in the pool area.
[0035] In case the MS is not attached to one cell, i.e., an Iupc
connection of a Standalone A-GPS SMLC (SAS) and the SRNC is in a
URA/GRA (RRA) paging state, the paging is sent to the whole paging
area that may include other BSCs/RNCs, and the Iu-r interface. A
Standalone A-GPS SMLC (SAS) is a logical node that provides GPS
related data to the RNC and may perform a position calculation (pc)
function. The Iupc interface is a logical interface for the
interconnection of a SAS and RNC components of the UTRAN.
[0036] When the MS is in an Idle mode, i.e., the MS is switched on
but does not have any established Radio Resource Control (RRC)
connection, upon receipt of a Paging Request message for a
circuit-switched service the MS may accept to respond to this
request. After establishing a RRC connection, known CS procedures
will be followed for the paging response. When received at the BSS,
the Paging Response message is to be routed to the MSC.
[0037] In this case, the serving BSC/RNC may store the CN identity
of the MSC originating the paging request so that the response from
paging returns to the correct CN. In general, however, the RRA
spans more than one BSC. If the paging response is routed through a
BSC/RNC in a pool area different from the SBSC, and relocation is
triggered to that RNC/BSC, the routing path for the paging response
will be changed, compared to the routing path for the paging
request. After changing the routing path, the originating CN will
be unknown to the radio access network nodes and core network nodes
involved. In this case, therefore, the paging response will not
arrive at the originating CN.
[0038] A recent solution approach to such paging issues suggests
including the MSC/VLR (Visitor Location Register) identity in a CS
paging message (3GPP, TSG GERAN #8 Tdoc GP-020492, Rev. Tdoc
GP-020360 Rome, Italy Feb. 4-8, 2002 Agenda item 6.6 and 7.2.5.1.4,
available at www.3gpp.org/ftp/Information/WI_Sheet/GP-020492.pdf).
By this method, the MS will know the address of the originating CN
and can, after suitable extraction from the paging message, include
this address into the signaling with the new SRNC/BSC after
relocation.
[0039] However, by including this additional information element in
paging messages the data load transported back and forth between
the MSC requesting the paging and the MS will be increased. Also,
additional procedures are necessary that allow the MS to extract
the identity from the paging message. This requires costly updating
of the software of the mobile stations subscribing to a network
implementing the solution mentioned above.
SUMMARY OF THE INVENTION
[0040] It is therefore an object of the present invention to
provide a network system and a simple method allowing to change a
routing path between a first data network and a mobile station
attached to a second data network that keeps necessary additional
data traffic in the networks involved at a low level. It is another
object of the present invention to provide a network system and a
method that allow changing a routing path between a first data
network and a mobile station attached to a second data network
without involving the mobile station in the pertaining
signaling.
[0041] Furthermore, it is an object of the present invention to
provide a network device for operation in a radio data network that
allows a change of the routing path between a first data network
and a mobile station attached to a second data network without
losing track of a network node in the first data network involved
in the previous routing path.
[0042] These objects are achieved by a method according to claim 1,
a network structure according to claim 22, and a network device
according to claim 33, respectively.
[0043] According to the method of the invention, the routing path
between a first data network and a mobile station attached to a
second data network is changed. Before the change the routing path
comprises at least one first network node in the first data
network, a second network node communicating with the first network
node, a third network node communicating with said second network
node, and the mobile station. After the change the routing path
comprises the first network node, the third network node
communicating with said first network node and the mobile
station.
[0044] According to the method of the present invention the
described change of the routing path is performed, wherein a step
of transferring an information element from said second network
node to said third network node is taken, said information element
comprising an identification element of said first network
node.
[0045] The mentioned order of the network nodes does not
necessarily reflect the direction of the actual routing. In paging
and subsequent paging response, for instance, the paging message
will originate at, or first pass, the first network node, and then
pass through the second and third network nodes to finally reach
the mobile station. The paging response, however, will originate at
the mobile station and end at the first network, in opposite order
to the order mentioned above. Thus, both routing paths before and
after the change, according to the invention, may be used in both
directions, from the mobile station to the first network node, or
from the first network node to the mobile station.
[0046] It is noted, however, that the best use is made of the
invention in situations when the order of the routing stations is
followed as in the paging/paging response example given above.
[0047] The change of the routing path allows reducing signaling
within the second data network that was necessary before the
change. The third network node in the second data network will be
able to communicate directly with the first network node in the
first data network, without requiring control or the additional
routing station of the second network node. This gain in signaling
capacity corresponds to that achieved by known relocation methods.
However, known relocation methods are not able to cope with the
situation of CS IMSI paging to a mobile station for which an Iu
signaling connection already exists in a network system supporting
Iuflex. Paging coordination is now possible in the above
scenario.
[0048] By applying the invention it is now possible to rout a
paging response message from a CS-paged mobile station back to the
first network node originating the paging request also in a network
system that supports Iuflex. Furthermore, the RRA can span more
than one RNC/BSC, and interworking between UTRAN and GERAN is
possible. This is because the third network node receives, in the
form of an information element, the CN node identification of the
first network note that originated the paging, and will use it for
routing the paging response back to the first network node.
[0049] In a preferred embodiment of the method of the invention the
information element containing the identification of the first
network node is transferred directly from said second network node
to said third network node. This is under most circumstances the
shortest path possible.
[0050] In an alternative preferred embodiment, the information
element is transferred from said second network node to at least
one fourth network node in said first data network and then from
said fourth network node to said third network node.
[0051] Both alternative embodiments mentioned allow to perform the
step of transferring the identification of the first network node
using known control messages by mere addition of the information
element, or even more simply by adding the first-network-node
id.
[0052] In the second alternative embodiment, said fourth network
node in the first data network preferably has a
serving-network-node function for the second network node. By a
serving-network-note function of a network node in the first
network the functionality corresponding to that of a SGSN in a core
network is meant. An SGSN has a serving-network-node function for
the RAN nodes in its service area regarding connections of MS
served by these RAN nodes.
[0053] The fourth network node may keep the role of a serving
network node after the change. This applies especially in network
systems supporting Iuflex, because here several SGSNs serve a RAN
node pool area in parallel.
[0054] However, in another embodiment of the method of the
invention, the serving-network-node function of the fourth network
node for the second network node regarding the connections of the
MS is transferred to a fifth network node that will take the role
of serving-network node for the third network node regarding the
connection of the MS. Therefore, in this embodiment, the
information element is transferred from the second network node to
at least one fourth network node in the first data network, then
from the fourth network node to a fifth network node in said first
data network, and the from said fifth network node to the third
network node.
[0055] In a preferred embodiment of the method of the invention
said first network node is related to a packet-switched domain of
said first network and said fourth and fifth network nodes are
related to a circuit-switched domain of said first network, or vice
versa. In this case, the method of the invention has the advantage
of allowing to route a paging response to a paging request from the
in the packet switched domain back to the CS network node from
which the paging request originated, while keeping a control
session in the PS domain. The Iu connection is assumed to exist to
PS domain and there is paging from CS domain, but all that is said
here is also applicable when swapping the domains.
[0056] In a further preferred embodiment, said second network node
has a serving-network-node function in the second data network for
the mobile station before the change of the routing path, and said
third network node has a serving-network-node function in said
second data network for the mobile station after said change. The
serving-network-node function meant here corresponds to that of a
Serving Radio Network Controller (SRNC) or Serving Base Station
subsystem Controller (SBSC) in a UTRAN or GERAN, respectively.
Thus, the method of the present embodiment may include a relocation
procedure such as a SRNS relocation procedure. Accordingly, the
third network node may in a further embodiment have a
drift-network-node function before said change that corresponds to
that of a drift RNC or drift BSC in a UTRAN or GERAN.
[0057] Most preferably a plurality of first and/or fourth and/or
fifth network nodes communicates in parallel with said second
network node before said change, and with said third network node
after said change. This is for instance the case in Iuflex
operation of network systems. The service provision by multiple CN
nodes within a pool-area enlarges the served area compared to the
service area of one CN node. This results in reduced inter CN node
updates, handovers and relocations and it reduces the HLR (Home
Location Register) update traffic. The configuration of overlapping
pool-areas allows to separate the overall traffic into different MS
moving patterns, e.g., pool-areas where each covers a separate
residential area and all the same city center. Other advantages of
multiple CN nodes in a pool-area are the possibility of capacity
upgrades by additional CN nodes in the pool-area or the increased
service availability as other CN nodes may provide services in case
one CN node in the pool-area fails.
[0058] Preferably, the method of the invention includes a further
step of (temporarily) saving said information element or said
identification element to a data storage device communicating with
said second network node before said step of transferring said
information element to said third network node. Saving the
identification element is necessary only when a paging request is
received by the second network node, especially an IMSI paging
request in the situation described above. In other cases the
originating network node will be clearly indicated by the
connection, for instance, with an SGSN.
[0059] A further embodiment includes an additional step of
(temporarily) saving said information element or said
identification element to a data storage device communicating with
the third network node after the step of transferring the
information element to the third network node.
[0060] The method is most preferably applied in network systems,
where said second data network is a radio data network, especially
a radio access data network connected to a core network. In this
embodiment, the second data network comprises preferably a GERAN or
a UTRAN.
[0061] The method may be applied in situations where said second
network node is related to the GERAN and said third network node is
related to the UTRAN, or vice versa. In that case the second
network node is a BSC and the third network node is a RNC, or vice
versa.
[0062] The method of the invention is most preferably used during
routing of response data to request data from the mobile station to
the first network node. The request data originate at said first
network node in the first data network. The said request data will
have been routed along the routing path mentioned above before said
change. The response data will according to this use of the
invention be routed along said routing path after the change.
[0063] Further advantageous developments are defined in the
dependent claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0064] In the following, the present invention will be described in
greater detail based on a preferred embodiment with reference to
the drawings figures, in which:
[0065] FIG. 1 shows in the form of a schematic diagram a network
system according to the invention; and
[0066] FIG. 2 shows in the form of a schematic diagram a procedure
for routing a paging message according to the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0067] A first preferred embodiment will now be described on the
basis of a network structure according to FIG. 1.
[0068] The network structure of FIG. 1 has a core network 10, a
radio access network (RAN) 12 of GERAN (e.g., GERAN release 5 or
higher) type, and a GERAN Registration area (GRA) 14 to which a
mobile station (MS) 16 is attached. GRA 14 will in the following
also be addressed by the more general term Radio Registration Area
(RRA).
[0069] Core network 10 comprises an MSC 18 and a first a second
SGSN 20 and 22, respectively. It is noted that CN 10 may comprise
additional network nodes; which are omitted in FIG. 1 for reasons
of simplicity. MSC 18 controls the CS-domain connections for MS 16.
MSC 18 provides a digital exchange able to perform all necessary
functions needed to handle calls to and from mobile station 16,
such as registration, authentication, location updating, and
handovers. Specifically, MSC 18 provides the call handling
necessary to cope with the mobile nature of MS 16, e.g. paging.
[0070] SGSNs 20 and 22 provide similar services to MS 16 in the
PS-domain as MSC 18 does in the CS-domain. Especially, SGSNs 20 and
22 keep track of the location of MS 16 and perform security
functions and access control. Since the network structure of FIG. 1
supports Iuflex functionality SGSNs 20 and 22 may serve several RAN
nodes in parallel in the PS domain.
[0071] GERAN 12 comprises two BSCs 24 and 26. Both BSCs 24 and 26
are in charge of controlling the use and the integrity of the radio
resources for mobile subscribers in RRA 14. They cooperate with
core network nodes and transceiver stations in RRA 14 in
establishing, maintaining and releasing a connection for MS 16.
[0072] Each BSC is connected to a set of BTSs in RRA 14. BSC 24 is
connected to BTSs 28 to 34 through Abis interfaces, BSC 26 is
connected to BTSs 36, 38, and 40, through Abis interfaces as well.
BTSs 28 to 34 form a service area for BSC 24, BTSs 36 to 40 form a
service area for BSC 26. The BTSs 28 through 40 provide radio
transmission and reception in cells. They may be adapted for IP
operation. Their main task is the conversion of data to and from MS
16. RRA 14 forms a Iuflex pool area for a CS domain served number
of transceiver stations grouped in an area within which a MS may
roam without need to change the serving CN node, i.e. the serving
SGSN or the serving MSC. The pool-areas of the CS and of the PS
domain are configured independently with the granularity of RAN
node service areas.
[0073] Inside GERAN 12 the BSCs 24 and 26 are interconnected
together through an Iur-g interface. Both BSCs are connected to MSC
18 through an A interface. They are connected to SGSNs 20 and 22,
respectively, through a Gb or an Iu.sub.PS interface each.
[0074] For the embodiment of FIG. 1 it is assumed that MS 16 is
camping on a cell under BSC 26, which takes the role of a drift
BSC. The serving BSC of MS 16 is assumed to be BSC 24. The control
connection of MS 16 is assumed to be in the PS domain. Thus,
serving BSC 24 is connected to the PS domain of CN 10 through an Iu
interface. Serving BSC 24 and drift BSC 26 are connected through
the Iur-g interface. That is, since the network structure of FIG. 1
supports Iuflex, SGSN 20 or both SGSNs 20 and 22 in parallel serve
RAN node 24.
[0075] It is further assumed that MS 16 is operated in the RRA_PCH
mode. In that mode, the user monitors a paging channel (PCH). The
RAN 12 knows the position of the mobile with the accuracy of the
registration area (RRA) 14 only. The exact cell the user is camping
on is not known since in this mode the MS 16 does not need to
signal every cell change. In this state MS 16 has only a logical
connection towards serving 24 BSC but is not consuming any physical
resources.
[0076] It is noted that the assumptions above are made for the
purposes of explaining the invention in the context of a simple
example. The invention is applicable in other circumstances as
well. For instance, the control connection of the RAN to the CN
could be in the CS domain. Also, either the drift BSC or the
serving BSC, or both, could be a RNC.
[0077] With reference to both FIGS. 1 and 2 it will be explained in
the following how the network system of FIG. 1 handles a paging
request from the CS domain. For simplification, the Iu connection
is assumed to exist to PS domain and there is paging from CS
domain, but all that is said here is also applicable when swapping
the domains.
[0078] When in the above situation a paging occurs to MS 16 from
the CS domain, MSC 18 sends a CS paging request to serving BSC 24
(step 1 in FIG. 2). The paging request may be an IMSI
(International Mobile Subscriber Identity) paging, i.e., the paging
message does not contain a TMSI (Temporary Mobile Subscriber
Identity). In case of Iuflex operation and paging with IMSI, the
BSC/RNC may store the Global CN identity of the CN node that
originated the paging, in order to send the paging response to the
correct CN node. The serving BSC 24 will, upon reception of the
paging from MSC 18, send the paging request to BTSs 28 to 40 in the
RRA. It will do it through the Abis interface using the BSAP (Base
Station Application Part) protocol to BTSs 28 to 34 for which it is
controlling BSC, and through the Iur-g interface using RNSAP (Radio
Network Subsystem Application Part) protocol to drift BSC 26 for
BTSs 36 through 40 controlled by the drift BSC (step 2 in FIG.
2).
[0079] MS 16 will respond to the paging by sending a Cell Update
message to the drift BSC 26 (step 3 in FIG. 2). Drift BSC 26 will
forward the Cell Update message to serving BSC 24 (step 4 in FIG.
2). This will trigger relocation. Uplink signaling transfer will be
performed between Target BSC 26 and Source BSC 24 (step 5 in FIG.
2). The relocation may include a different SGSN, e.g. SGSN 22. The
relocation procedure is started by sending a "Relocation Required"
message from SBSC 24 to SGSN 20 (step 6). SBSC 24 is in the present
context also named a source BSC. SGSN 20 will forward the
relocation request to SGSN 22 controlling drift BSC 24 (step 7).
SGSN 22 sends a "Relocation Request" message to drift BSC 24 (step
8), which in this context is also named a target BSC. Target BSC 24
will respond by sending a "Relocation Request Acknowledge" message
after establishing radio access bearers (step 9). This message will
be forwarded from SGSN 22 to SGSN 20 (step 10), which in turn sends
a "Relocation Command" message to SBSC 24 (step 11).
[0080] Source BSC 24 will start forwarding data for radio access
bearers to the target BSC 26. The data may alternatively be
transferred as duplicate using the Iu interface, i.e., routed
through the core network nodes 20 and 22. Source BSC 24 will
continue receiving uplink data and transmitting duplicates of
downlink data (step 12).
[0081] After the start of forwarding data, and possibly while
continuing this working on this step, source BSC 24 will send a
"Relocation commit" message to target BSC 26. This will trigger the
execution of the relocation of the serving BSC from source BSC 24
to target BSC 26. In this message SRNS contexts will be forwarded
using the "Forward SRNS Context" message and the RANSAP protocol to
target BSC 24 (step 13).
[0082] According to the present embodiment of the method of the
invention, source BSC 24 will in this step also transmit the CN
node identity (id) of MSC 18 originating the paging request, along
with the SRNS contexts. The id may be an additional parameter of
the SRNS context message. The CN node id parameter may be a Network
Resource Identifier (NRI), which identifies uniquely an individual
CN node out of all CN nodes, which serve in parallel a
pool-area.
[0083] According to an alternative embodiment of the method of the
invention, source BSC 24 will in step 6 transmit the CN node id of
MSC 18 originating the paging request, along with the "Relocation
Required" Message using the RANAP protocol to SGSN 22. SGSN 22 will
forward the CN node id in step 8 along with or as a parameter of
the "Relocation Request" Message to target BSC 26.
[0084] Target BSC 26 will send a "Relocation Detect" message to
SGSN 22, a "Cell update-Confirm" message to MS 16 and, finally, a
"Relocation Complete" message to SGSN 22 (steps 14 to 16). SGSN 22
will forward the Relocation Complete message to SGSN 20, which will
acknowledge this (steps 17, 18). In the following, SGSN 20 will
release the Iu connection to source BSC 24, which will acknowledge
by sending an "Iu release complete" message back to new SGSN 22
(steps 19, 20).
[0085] The mobile station will now be able to respond to the paging
request by sending a paging response message to new SBSC 26 (step
21). Since BSC 26 knows the id of MSC 18 the paging response will
be forwarded to MSC 18 through the A interface (step 22).
[0086] It is noted that the present invention is not restricted to
the specific features of the above-preferred embodiment, but can be
used in all types of communications networks such as GSM systems
including circuit switched or packet switched systems. The
invention is of course also applicable to any other communication
network effecting mobile or fixed communication. Particularly, the
invention is also applicable to pure packet switched networks like
the future IP-based networks. Any kind of party's identifier data
and party's equipment identifier data may be stored in the
database, based on which the correspondence is checked and new
entries are added. The preferred embodiment may thus vary within
the scope of the attached claims.
* * * * *
References